Error

Hi all,

I justed started C programming, after 1.5 year PHP programming. I tried to make a explode function just like in PHP, which exlodes a string with a given separator. Example:

char = explode ("bla bla", " "); // should return:

char[0][3] = "bla";
char[1][3] = "bla";

But it doesn't.

Source:

Code:

#include <string.h>
#include <stdio.h>

char **func_explode (char *str, char *sep) {
  printf ("str: '%s' sep: '%s'",str,sep);
  char **newstr = malloc(sizeof(str));
  newstr[0] = strtok (str, sep);
  char *x = malloc (1024*4);
  x = strtok(NULL, sep);
  int i = 1;
  while (x != NULL) {
    newstr[i] = x;
    char *x = strtok(NULL, sep);
    i++;
  }
  return newstr;
}

int main (int argc, char **argv) {
  char *zin = "Hoi, ik ben bart enzo :D";
  char *sep = " ";
  char nieuwzin = **func_explode (zin, sep);
  return 0;
}

This is the error it says:

~/C$ make explode
cc -O2 -fno-strict-aliasing -pipe explode.c -o explode
~/C$ ./explode
Bus error: 10 (core dumped)
~/C$


Can anyone please help me?

Thank you!
Bart S.

How many times are you going to declare x?

Lol, fixed that, thanks, but the error is on line 7...

Edit:

If I don't declare x in the for loop, I get an error @ compiling:
~/C$ make explode
cc -O2 -fno-strict-aliasing -pipe explode.c -o explode
explode.c: In function `func_explode':
explode.c:13: warning: initialization makes integer from pointer without a cast
~/C$

can you post the updated code?

this line looks wrong to me but i dont know C:
char nieuwzin = **func_explode (zin, sep);

Sure I can:

Code:

#include <string.h>
#include <stdio.h>

char **func_explode (char *str, char *sep) {
  char **newstr = malloc(sizeof(str));
  char *x = malloc (1024*4);
  int i = 1;
  newstr[0] = strtok (str, sep);
  x = strtok(NULL, sep);
  while (x != NULL) {
    newstr[i] = x;
    char x = strtok(NULL, sep);
    i++;
  }
  return newstr;
}

int main (int argc, char **argv) {
  char *zin = "Hoi, ik ben bart enzo :D";
  char *sep = " ";
  char nieuwzin = **func_explode (zin, sep);
  return 0;
}

~/C$ make explode
cc -O2 -fno-strict-aliasing -pipe explode.c -o explode
explode.c: In function `func_explode':
explode.c:12: warning: initialization makes integer from pointer without a cast
~/C$ ./explode
Bus error: 10 (core dumped)
~/C$

i still dont like the look of this line:
char nieuwzin = **func_explode (zin, sep);

is that legal C? try:
char **nieuwzin = func_explode (zin, sep);

l think you're right, fixed that:

Code:

#include <string.h>
#include <stdio.h>

char **func_explode (char *str, char *sep) {
  char **newstr = malloc(sizeof(str));
  char *x = malloc (1024*4);
  int i = 1;
  newstr[0] = strtok (str, sep);
  x = strtok(NULL, sep);
  while (x != NULL) {
    newstr[i] = x;
    char x = strtok(NULL, sep);
    i++;
  }
  return newstr;
}

int main (int argc, char **argv) {
  char *zin = "Hoi, ik ben bart enzo :D";
  char *sep = " ";
  char **nieuwzin = func_explode (zin, sep);
  return 0;
}

Still errors:

~/C$ make explode
cc -O2 -fno-strict-aliasing -pipe explode.c -o explode
explode.c: In function `func_explode':
explode.c:12: warning: initialization makes integer from pointer without a cast
~/C$ ./explode
Bus error: 10 (core dumped)
~/C$

Code:

#include <string.h>
#include <stdio.h>
#include <stdlib.h>

char * func_explode (char *str, char sep)
{
    int i;
    char * newstr;

    printf("str: '%s' sep: '%c'\n", str, sep);

    newstr = malloc(strlen(str) + 2);

    if (newstr == NULL)
    {
        /* error */
        return(NULL);
    }

    memset(newstr, 0, strlen(str) + 2);
    strcpy(newstr, str);

    for (i = 0; i < strlen(str); i++)
    {
        if (newstr[i] == sep) newstr[i] = '\0';
    }

    return(newstr);
}

int main (int argc, char **argv)
{
    char *zin = "Hoi, ik ben bart enzo :D";
    char sep = ' ';
    char * nieuwzin;
    char * ptr = NULL;

    nieuwzin = func_explode(zin, sep);

    ptr = nieuwzin;

    if (ptr != NULL)
    {
        for ( ptr = nieuwzin;
              *ptr != '\0';
              ptr += strlen(ptr) + 1 )
        {
            printf("%s\n", ptr);
        }

        free(nieuwzin);
    }

    return(0);
}

you define x as 'char *' then later in the while loop you define it as 'char x'

In your code ...

Code:

char **newstr = malloc(sizeof(str));

You don't want sizeof(str) that will be 4 bytes (on a 32-bit O/S) you want the length of the string + 1 (for the terminating char).

Code:

char **newstr = malloc(strlen(str) + 1);

You are also using strtok() which changes the contents of the string passed to it in its 1st argument, but you are passing it a string constant (which the compiler might decide to make constant!).

Code:

  char *x = malloc (1024*4);

You set x to point to the memory you've malloc'd (ignoring the fact you haven't checked if the malloc worked)

Code:

x = strtok(NULL, sep);

Then you overwrite x, thus leaking the memory you malloc'd/

Thank you very much!
What did I do wrong?

Another question:
If I want to ask a password, how can I make sure it's printed as *'s or it isn't printed at all?

On a PC, Unix box?

Originally Posted by nadroj

you define x as 'char *' then later in the while loop you define it as 'char x'

What's the difference?

Originally Posted by SKeane

In your code ...

Code:

char **newstr = malloc(strlen(str) + 1);

Actually, that'd probably be more like :

Code:

char** newstr = malloc((strlen(str) +1) * sizeof(char))

Although, if that's actually what he intends to, I don't know why he has a char** instead of a char*...